dccp: Implement both feature-local and feature-remote Sequence Window feature

This adds full support for local/remote Sequence Window feature, from which the
  * sequence-number-validity (W) and
  * acknowledgment-number-validity (W') windows
derive as specified in RFC 4340, 7.5.3.

Specifically, the following is contained in this patch:
  * integrated new socket fields into dccp_sk;
  * updated the update_gsr/gss routines with regard to these fields;
  * updated handler code: the Sequence Window feature is located at the TX side,
    so the local feature is meant if the handler-rx flag is false;
  * the initialisation of `rcv_wnd' in reqsk is removed, since
    - rcv_wnd is not used by the code anywhere;
    - sequence number checks are not done in the LISTEN state (cf. 7.5.3);
    - dccp_check_req checks the Ack number validity more rigorously;
  * the `struct dccp_minisock' became empty and is now removed.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 18 insertions, 24 deletions

diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index f2230fc168e1..04ae91898a68 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -409,23 +409,21 @@ static inline void dccp_hdr_set_ack(struct dccp_hdr_ack_bits *dhack,
 static inline void dccp_update_gsr(struct sock *sk, u64 seq)
 {
         struct dccp_sock *dp = dccp_sk(sk);
-        const struct dccp_minisock *dmsk = dccp_msk(sk);
 
         dp->dccps_gsr = seq;
-        dccp_set_seqno(&dp->dccps_swl,
-                       dp->dccps_gsr + 1 - (dmsk->dccpms_sequence_window / 4));
-        dccp_set_seqno(&dp->dccps_swh,
-                       dp->dccps_gsr + (3 * dmsk->dccpms_sequence_window) / 4);
+        /* Sequence validity window depends on remote Sequence Window (7.5.1) */
+        dp->dccps_swl = SUB48(ADD48(dp->dccps_gsr, 1), dp->dccps_r_seq_win / 4);
+        dp->dccps_swh = ADD48(dp->dccps_gsr, (3 * dp->dccps_r_seq_win) / 4);
 }
 
 static inline void dccp_update_gss(struct sock *sk, u64 seq)
 {
         struct dccp_sock *dp = dccp_sk(sk);
 
-        dp->dccps_awh = dp->dccps_gss = seq;
-        dccp_set_seqno(&dp->dccps_awl,
-                       (dp->dccps_gss -
-                        dccp_msk(sk)->dccpms_sequence_window + 1));
+        dp->dccps_gss = seq;
+        /* Ack validity window depends on local Sequence Window value (7.5.1) */
+        dp->dccps_awl = SUB48(ADD48(dp->dccps_gss, 1), dp->dccps_l_seq_win);
+        dp->dccps_awh = dp->dccps_gss;
 }
 
 static inline int dccp_ack_pending(const struct sock *sk)
diff --git a/net/dccp/feat.c b/net/dccp/feat.c
index 67ffac9905f8..7303f79705d2 100644
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -51,8 +51,17 @@ static int dccp_hdlr_ccid(struct sock *sk, u64 ccid, bool rx)
 
 static int dccp_hdlr_seq_win(struct sock *sk, u64 seq_win, bool rx)
 {
-        if (!rx)
-                dccp_msk(sk)->dccpms_sequence_window = seq_win;
+        struct dccp_sock *dp = dccp_sk(sk);
+
+        if (rx) {
+                dp->dccps_r_seq_win = seq_win;
+                /* propagate changes to update SWL/SWH */
+                dccp_update_gsr(sk, dp->dccps_gsr);
+        } else {
+                dp->dccps_l_seq_win = seq_win;
+                /* propagate changes to update AWL */
+                dccp_update_gss(sk, dp->dccps_gss);
+        }
         return 0;
 }
 
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index 6821ae33dd37..5ca49cec95f5 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -42,11 +42,6 @@ struct inet_timewait_death_row dccp_death_row = {
 
 EXPORT_SYMBOL_GPL(dccp_death_row);
 
-void dccp_minisock_init(struct dccp_minisock *dmsk)
-{
-        dmsk->dccpms_sequence_window = sysctl_dccp_feat_sequence_window;
-}
-
 void dccp_time_wait(struct sock *sk, int state, int timeo)
 {
         struct inet_timewait_sock *tw = NULL;
@@ -110,7 +105,6 @@ struct sock *dccp_create_openreq_child(struct sock *sk,
                 struct dccp_request_sock *dreq = dccp_rsk(req);
                 struct inet_connection_sock *newicsk = inet_csk(newsk);
                 struct dccp_sock *newdp = dccp_sk(newsk);
-                struct dccp_minisock *newdmsk = dccp_msk(newsk);
 
                 newdp->dccps_role           = DCCP_ROLE_SERVER;
                 newdp->dccps_hc_rx_ackvec   = NULL;
@@ -128,10 +122,6 @@ struct sock *dccp_create_openreq_child(struct sock *sk,
                  *    Initialize S.GAR := S.ISS
                  *    Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
                  */
-
-                /* See dccp_v4_conn_request */
-                newdmsk->dccpms_sequence_window = req->rcv_wnd;
-
                 newdp->dccps_gar = newdp->dccps_iss = dreq->dreq_iss;
                 dccp_update_gss(newsk, dreq->dreq_iss);
 
@@ -290,7 +280,6 @@ int dccp_reqsk_init(struct request_sock *req,
         inet_rsk(req)->rmt_port   = dccp_hdr(skb)->dccph_sport;
         inet_rsk(req)->loc_port   = dccp_hdr(skb)->dccph_dport;
         inet_rsk(req)->acked      = 0;
-        req->rcv_wnd              = sysctl_dccp_feat_sequence_window;
         dreq->dreq_timestamp_echo = 0;
 
         /* inherit feature negotiation options from listening socket */
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 945b4d5d23b3..314a1b5c033c 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -174,8 +174,6 @@ int dccp_init_sock(struct sock *sk, const __u8 ctl_sock_initialized)
         struct dccp_sock *dp = dccp_sk(sk);
         struct inet_connection_sock *icsk = inet_csk(sk);
 
-        dccp_minisock_init(&dp->dccps_minisock);
-
         icsk->icsk_rto          = DCCP_TIMEOUT_INIT;
         icsk->icsk_syn_retries  = sysctl_dccp_request_retries;
         sk->sk_state            = DCCP_CLOSED;